The ZX Spectrum+ 128Kexpansion connector is a double sided card edge connector with a 0.1 inch spacing. The two rows of conductors are numbered from right to left looking into the rear of the computer.
One pair of conductors are missing as there is an indexing slot cut out of the circuit board.

Power

Upper Pin 20 is connected to the −5 volt DC output of the internal power supply circuitry.

Upper Pin 22 is connected to the +12 volt DC output of the internal power supply circuitry.

Upper Pin 23 is connected to the oscillating voltage within the internal power supply circuitry. This is nominally 12 volts AC.

Lower Pins 6, 7, and 14 are connected to the 0 volt rail.

Removed Video Outputs

Unlike the ZX Spectrum 16K/48K the ZX Spectrum+ 128KULA generates RGB and Bright video signals rather than intensity and colour difference signals. The Y, U, and V signals are therefore not available so the pins previously used for them are left unconnected. Additionally the composite video signal has been removed.